1. Field of the Invention
The present invention relates to a method of forming an aqueous coating on a plastic sheet surface for vehicle interior equipment, and more particularly, to a method of forming an aqueous coating on a plastic sheet surface by performing a coating process in two steps on the plastic sheet.
2. Background
In general, extrusion sheets or calendaring sheets made of polyvinylchloride (PVC) or polyvinylchloride (PVC)/acrylonitrile butadiene styrene (ABS) copolymer have been widely used as surface materials of vehicle interior parts, such as instrument panel, door trim panel, headlining, etc. However, such sheets include a great quantity of organic solvents that cause odors inside the vehicle, volatile organic compounds, etc. The volatilities and some compounds included in paints may adversely affect users health, resulting in decreased scope of users choice.
Recently, such sheets including organic solvents have been rapidly substituted with thermoplastic polycarbonate urethane (“TPO”) sheets. TPO sheets are advantageous in terms of environmental friendliness, light-weightiness, fogging, low-temperature impact toughness and odor.
Surface materials for vehicle interior equipment are generally subjected to a surface coating process to improve their physical properties such as friction and wear resistance, chemical properties such as chemical resistance, solvent resistance, etc., light resistance. Surface coating process also serves to lower gloss for ensuring driver's visual field appropriately. It also serves to unify the color of peripheral parts.
Conventionally, as depicted in FIG. 1, TPO sheets are coated by three steps: pretreatment coating, base coating and top coating. More particularly, a TPO sheet is subjected to pretreatment, such as surface treatment including flame process, ozone process, plasma process, etc., or oil primer treatment with chlorinated polyolefin resins. The pretreated sheet is subjected to base coating material of acrylic resins and then a top coating material of urethane resins. This is why the TPO sheet shows inferior adhesion property due to its non-polarization and high crystallization in terms of molecular structure.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.